Prior to the instant invention, endless belts have frequently been used in various industrial operations as a carrying means for many materials. Examples of such endless fabrics include heavy duty belts for transporting merchandise or produce from a warehouse to railcars or trucks, carrying belts for packaging or mail routing, filter fabrics for use in dewatering sludge resulting from the treatment of wastes, belts for use as filter fabrics for removing materials from air streams or for carrying water in humidification processes, and belts for use in papermaker fabrics such as press felts, press fabrics, forming wires and for use in dryer fabrics on a paper or other forming machine.
The present invention relates to those belts which can be utilized for the aforesaid purposes and which are formed in an endless loop, and to the method and construction by which the ends of the belt are joined together to form the endless loop. Heretofore, the fabric for endless belts was made in an endless form prior to installation; and since the fabric was endless, the operating machinery used in conjunction therewith had to be partially dismantled so that the fabric could be slipped or threaded onto the machine. Obviously, this was a slow, expensive and often dangerous method of installation in that the endless fabric was often heavy and stiff. To simplify these conditions, many fabrics have been made as an open belt, i.e., not endless, but with specifically formed ends which can accept a pintle wire for joining them when the ends are brought together, thereby making the fabric endless. In most cases, it is easier to thread a flat, open-ended fabric through a machine, and once the fabric is threaded around the rolls, to join it together making it endless. In many instances fabrics have been made endless by incorporating appropriate construction means into fabric, whereby special loops of yarn are formed at the fabric ends, the loops from both ends of the fabric thereafter being intermeshed and joined together by a pintle wire or pin that projects through the loops of yarn. Other fabric joining methods have also included the use of separately attached loop materials such as spiral wires or metal clips.
As described, one of the advantages of joining fabrics by a loop seam type joint is that heavy, cumbersome fabrics may be more easily installed on the operating machinery. As an example, fabrics, such as a press felt as used on a paper machine, may weigh as much as 1200 pounds and measure greater than 400 feet in length or greater than 400 inches in width. Although a loop seam facilitates the installation of such a fabric, the loop seam must be strong enough to withstand the tensional forces of the machine on which it is installed, and in some circumstances be open sufficiently in structure to maintain porosity normal to the body of the felt in those applications which require absolute uniformity. Examples of seamed-type fabrics as used in prior known papermaker felts and of which the applicant is aware are illustrated in U.S. Pat. Nos. 4,698,250, 4,695,498; 4,574,435; 4,250,822; 4,123,022; 4,026,331; 4,006,760; 3,815,645; 3,653,097; 3,283,388 and 2,883,734.
One of the problems experienced with the prior known loop seam construction as used in papermaking felts that utilize warp yarns to form the seam is that the seam would often fail after limited use of the felt which was usually caused by slippage and extension of the loop structure under tension due to the weave pattern or method of construction. This resulted in the loops being weakened with the eventual failure of the felt.
As will be described, the construction of the instant invention is not dependent upon any special weave pattern, and the binding loops cannot be pulled from the felt by excessive tension because they are formed as an integral part of the body of the felt.